Light stable polymeric compositions



United States Patent 6 3,000,855 LIGHT STABLE POLYMERIC COMPOSITIONS Gerald A. Clark and Carl B. Havens, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Original application Apr. 23, 1956, Ser. No. 579,771, now Patent No. 2,891,996, dated June 23, 1959. Divided and this application Sept. 24, 1958, Ser. No. 762,944

5 Claims. (Cl. 260-4595) This invention relates to polymeric compositions having improved stability to light. More particularly, it relates to a new class of organic compounds finding utility as light stabilizers for haloethylene polymers.

This application is a division of our copending application, U.S. Serial No. 579,771, filed April 23, 1956, now U.S. Patent No. 2,891,996, issued June 23, 1959.

Haloethylene polymers, such as the polymers and copolymers of vinyl chloride and of vinylidene chloride are known to be highly sensitive to the effects of elevated temperatures and of light and under prolonged exposure to heat and light may become so degraded as to be commercially useless. It has been common practice to blend certain compounds with the polymer to stabilize it against the degradative effects of heat and light. Several of such compounds, however, are colored materials which impart an objectionable initial color to the stabilized composition and thus prevent the production of a commercially salable white composition.

Still other disadvantages of many of the previous compounds are a high odor level and volatility. Any odor in the stabilizer will be transferred to the stabilized composition. When volatile stabilizers are employed, the stabilizers volatilize out of the composition, leaving the composition in time unprotected against the degradative effects of light, particularly ultra-violet light. In addition, all of the compounds vary in their ability to absorb ultra-violet light and it is impossible to predict the eifectiveness of any particular compound with any degree of certainty, and some of the compounds lose some of their efiectiveness for absorbing ultra-violet light over a prolonged period of time.

In view of the above problems it would be desirable and it is the principal object of this invention to provide a polymeric composition stabilized against the degradative effects of light by means of such compounds.

It is a further object to provide such compositions which have little or no initial color and have a low odor level.

Another object is to provide a group of such compositions which have low volatility.

The above and related objects are achieved by utilizing as the light stabilizers in the compositions a group of 2,4-dihydroxy benzophenone derivatives having the general formula:

wherein one X is an organic acyl group derived from a carboxylic acid having from 1 to 8 carbon atoms and the remaining X is selected from the group consisting of hydrogen and organic acyl groups derived from carboxylic acids having from 1 to 8 carbon atoms. The invention specifically includes stabilized thermoplastic compositions comprising such compounds and haloethylene polymers.

As typical examples of the compounds which are within the scope of this invention may be mentioned:

7 3,000,855 Patented Sept. 19, 1961 ice 3-acetyl-2,4-dihydroxy benzophenone 5-acetyl-2,4-dihydroxy benzophenone 3,5-diacetyl-2,4-dihydroxy benzophenone 3-acetyl-5-benzoyl-2,4-dihydroxy benzophenone 3-benzoyl-5-acetyl-2,4-dihydroxy benzophenone 3-butyryl-2,4-dihydroxy benzophenone 3-caprylyl-2,4-dihydroxy benzophenone 3-benzoyl-S-caprylyl-2,4-dihydroxy benzophenone 3,5-dibutyryl-2,4-dihydroxy benzophenone 3,S-dicaprylyl-2,4-dihydroxy benzophenone The compounds are easily prepared from readily available materials. As a typical example of their preparation the procedure for preparing 3-acetyl-2,4-dihydroxy benzophenone will be described. A reaction mixture consisting of 0.25 mole of acetyl chloride, 0.25 mole of 4-benzoyl resorcinol, and 0.5 mole aluminum chloride in 250 mls. of orthodichlorobenzene was heated to 120 C. for one hour. The reaction mixture was then cooled and poured into cold dilute HCl. The solvent was removed by distillation and the product distilled in vacuo at 0.5 mm. Hg. The fraction boiling at l-187 C. was collected, cooled, and recrystallized three times from percent ethyl alcohol. The 2-acetyl-4-benzoyl resorcinol was in the form of pale yellow crystals melting at 99.5 to C. The compound 3,5-diacetyl-2,4-dihydroxy benzophenone prepared in a similar manner was found to be a white crystalline solid melting at l51151.5 C.

The compounds of this invention find utility as light stabilizers for haloethylene polymers, and especially chloroethylene polymers. By the term, chloroethylene polymers, it is meant to include those polymeric materials having a carbon chain to which are appended chlorine atoms. Typical examples of such compounds are the polymers of vinyl chloride and of vinylidene chloride and the copolymers and terpolymers containing either vinyl chloride or vinylidene chloride. Because the light stability problem is particularly troublesome with those polymeric materials containing predominantly polymerized vinylidene chloride units, these are preferred species. Because of their low degree of odor and color they produced compositions that were more merchandisabile than compositions prepared from previous stabilizers.

The effectiveness of the stabilizers will be more apparent from the following illustrative example wherein all parts are by weight.

Example A series of samples was prepared from a basic formulation consisting of 89.3 parts of a copolymer prepared from 85 percent vinylidene chloride and 15 percent vinyl chloride, 7 parts of a pentaerythritol tetraester of a mixture of saturated fatty acids (ave. chain length6) as a plasticizer, 1.7 parts of a phosphate heat stabilizer, and 1 pant titanium dioxide as a pigment. One sample was left as a blank for comparison. To another was added 1 part of 2-hydroxy-5-chlorobenzophenone, a known light stabilizer. To the others was added one part of the stabilizer of this invention. The samples were compression molded to form sheets 0.01 inch thick. The moldings were exposed to direct sunlight in the State of Arizona until an arbitrary standard of browning had been reached. The results are listed in the following table:

Ultra-violet sun hours to reach standard browning Stabilizer It can be seen that the compounds of this invention are about twice as effective as light stabilizers as is one of the most eifective previously known compounds.

The compounds will stabilize other haloethylene polymers including vinylidene chloride polymers and copolymers and vinyl chloride polymers and copolymers. The most useful range of concentration of the new compounds in such compositions is from 0.25 to 6 percent by weight.

What is claimed is:

1. A thermoplastic composition comprising a thermoplastic chloroethylene polymer containing essentially at least one polymerized monomer selected from the group consisting of vinylidene chloride and vinyl chloride and from 6 to 0.25 percent of the weight of said polymer of a stabilizer having the general formula:

OH i X wherein one X is an organic aliphatic acyl group derived from a carboxylic acid having from 1 to 8 carbon atoms and the remaining X is selected firom the group consisting of hydrogen and organic aliphatic acyl groups derived 4 from carboxylic acids having from 1 to 8 carbon atoms.

2. A thermoplastic composition as claimed in claim 1, wherein said stabilizer is 3-acetyl-2,4-dihydroxy benzophenone.

3. A thermoplastic composition as claimed in claim 1, wherein said stabilizer is 3,5-diacetyl-2,4-dihydroxy benzophenone.

4. A thermoplastic composition as claimed in claim 1, wherein said chloroethylene polymer is a copolymer of vinylidene chloride and a monoethylenically unsaturated comonomer wherein said polymer is composed predominantly of polymerized vinylidene chloride units.

5. A thermoplastic composition as claimed in claim 4, wherein said monoethylenically unsaturated comonomer is vinyl chloride.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Perkin et al.: Chem. Abstracts, vol. 1, p. 577 (1907). Bogert et al.: I. Am. Chem. Soc., vol. 52, pp. 837-50 (1930). 

1. A THERMOPLASTIC COMPOSITION COMPRISING A THERMOPLASTIC CHLOROETHYLENE POLYMER CONTAINING ESSENTIALLY AT LEAST ONE POLYMERIZED MONOMER SELECTED FROM THE GROUP CONSISTING OF VINYLIDENE CHLORIDE AND VINYL CHLORIDE AND FROM 6 TO 0.25 PERCENT OF THE WEIGHT OF SAID POLYMER OF A STABILIZER HAVING THE GENERAL FORMULA: 